Steam offers two branches. The main "stable" branch and the development branch.

You can swap between them with a very small download.

What is the beta branch
The latest (semi-finished) features released to eager players for testing. Only use the beta branch if you are familiar with From The Depths and want to help hunt for bugs. Expect from time to time serious game breaking bugs that might take a few days to fix. You may not want to permanently be in the beta branch.

What is the stable branch
Slightly older features (approximately one or two weeks) once they have been play tested and polished

Other notes
If you are planning on making a review / video then I'd personally appreciate you using the stable branch.

How to change branch
Right click "From The Depths" in your Steam library. Select Properties. Go to the BETAS tab. enter the access code "12charactersminimum". Select the development beta from the drop down list. Simply select "NONE" in this list to return to the stable branch.

*update 11-12-2015* Dev-Test notes
There is also a Dev-Test branch which is a less stable version of the development branch where we test all the new bits before moving it to development/stable branch. Expect things to break if your in this branch; backing up your game profile is recommended as a precaution.

How to change to Dev-Test Branch
Right click "From The Depths" in your Steam library. Select Properties. Go to the BETAS tab. enter the access code "onlymeonlyme,". Select the development beta from the drop down list. Simply select "NONE" in this list to return to the stable branch.